Rana, Evan, Kiwamu, Alexa

Tonight we worked on the ASC WFS again. We noticed that the P,Y had different integrators loaded even though they were named the same thing. There was also a high frequency gain of -30dB in the integretor. We have adjusted this filter (see attached photo of the new filter FM1, and second image with FM1 and FM2 on). We also aborbed some of the overall filter gain in FM1, so that the gains are not as small as before. We can now close the loops for PRMI, and they are stable. The configuration is as follows:

We noticed that there is a bit of coupling between the REFL_A_RF9_I pitch and yaw signal; however if the DC alignment is suffeciently good the loop is still stable. The ASC WFS then bring POPAIR_B_RF18_I_MON to ~170cts. These changes are reflected in the guardian. (The old gains are commented out, and the old FM1 filters remain in the SRCL loop in case we need to revert anything).

We continued on to DRMI. The PRCL loop worked fine. However, the above configurations for MICH failed. The loops would drive the BS cntrl too far off too quickly, and we would lose lock. Unfortunately, the DRMI lock acquisition time is extremely long, and trying to adjust this loop was difficult. We got tired....

Rana, Kiwamu

In order to study why the DRMI seems to lock faster at 1 Watt (see alog 14508), we checked the RF level of REFLAIR_A which is the one we use for acquiring lock of the DRMI.

The RF level at the output of the PD can be as high as -5 dBm and 3 dBm at maximum for 9 and 45 MHz respectively. This may be a bit too high, but certainly not outrageously too high.

(some details)

We hooked up a 300 MHz oscilloscope to the RF mon of the demod boards and checked the RMS value of the RF signals when the DRMI was flashing. Using the trigger on the scope, we captured two incidents where the RF level was high as follows:

• case 1 (triggered by the 45 MHz signal):
  • 9.29 mV rms or -27.6 dBm at 9 MHz
  • 21.8 mV rms or -20.2 dBm at 45 MHz
• case 2 (triggered by the 9 MHz signal):
  • 9.32 mV rms or -27.6 dBm at 9 MHz
  • 8.78 mV rms or -28.1 dBm at 45 MHz

Since the attenuation from the RF input to the RF mon on the demod board is 23 dBm, the real input signals must have been bigger by 23 dB than what we observed on the scope. Therefore the highest signals we expect at the output of the RFPD are -5 dBm and 3 dBm at 9 and 45 MHz respectively.

Note that when the DRMI was locked, there was almost no RF signals. We occasionally saw small signal of about -40 dBm at 45 MHz which we think was some kind of seismic excitation.

Jeff, Rana, Alexa, Kiwamu, Evan

Rana noticed that the BS oplev spectra (pitch and yaw) were suspiciously flat, perhaps indicating that they were dominated by ADC noise.

To fix this, Rana and I attached a DIP-switch jumper board (D1001631v2) to the 37-pin dsub on the BS oplev whitening board. This allows us to set bits that control the gain and whitening.

For each of the four segments, we flipped bits 2 and 4 (which increases the gain) and bit 5 (which engages a single whitening stage) to high; all others are low. Then we engaged the antiwhitening filters for each segment.

The first attachment shows the BS oplev spectra before (green, brown) and after (cyan, magenta) the gain+whitening+antiwhitening, with the loop off. We now appear to be resolving more features in the spectra.

The second attachment shows the BS oplev spectra after gain+whitening+antiwhitening, with the loop off (cyan, magenta) and on (red, blue).

J. Kissel

I've installed the refined alignment slider gains from 14405, and subsequently measured the optical lever calibration gain refinement for H1SUSETMX and H1SUSETMY using the method described in LHO aLOGs 14387 and 14312. I attach fits to the data points. The newly refined oplev calibration gains are 
EX P = 81.2  [urad/ct]
   Y = 115.2 [urad/ct]
EY P = 77.94 [urad/ct]
   Y = 53.55 [urad/ct]
Further, I've installed the already-computed, refined optical lever calibration gains for H1SUSBS from LHO aLOG 14387, compensated for the change in the optical lever damping loops, and confirmed the loop is still functional.

I've captured new safe.snaps for all three suspensions to ensure these values stick.

As such, all core-optic, BSC suspensions have optical lever gains refined precisely to a few hundredths of a percent (i.e. the separation of the baffle diodes, ~30 [cm] over the length of the arms 4 [km].)

Details

The ETMX P fitted correction factor is:
0.8805 ["urad"/urad]
The new ETMX oplev P calibration should be:
71.5 ["urad"/ct] * 1.136 [urad/"urad"] = 81.2 [urad/ct]
The ETMX Y fitted correction factor is:
1.058 ["urad"/urad]
The new ETMX oplev Y calibration should be:
121.8 ["urad"/ct] * 0.9455 [urad/"urad"] = 115.2 [urad/ct]
The ETMY P fitted correction factor is:
1.225 ["urad"/urad]
The new ETMY oplev P calibration should be:
95.5 ["urad"/ct] * 0.8161 [urad/"urad"] = 77.94 [urad/ct]
The ETMY Y fitted correction factor is:
1.295 ["urad"/urad]
The new ETMY oplev Y calibration should be:
69.33 ["urad"/ct] * 0.7724 [urad/"urad"] = 53.55 [urad/ct]

The raw measurement data and script to process it can be found here:

/ligo/home/jeffrey.kissel/2014-10-22/
calibratebsoplev_20141021.m
2014-10-22_H1SUSETMX_OplevCalibration_P_Offsets_10sec_avg.txt
2014-10-22_H1SUSETMX_OplevCalibration_Y_Offsets_10sec_avg.txt
2014-10-22_H1SUSETMY_OplevCalibration_P_Offsets_10sec_avg.txt
2014-10-22_H1SUSETMY_OplevCalibration_Y_Offsets_10sec_avg.txt

9:23 am, Filiberto to X-End station to pick up tools then to head to work at the Y-End station, also fix the seismometer.
9:30 am, Aaron to the X-End station to terminate a cable.
10:17 am, Karen to Y-End and Y-Mid stations, cleaning duties.
11:10 am, Betsy to the CS VEA, look for items by the PSL area.
11:30 am, Betsy exits CS VEA.
11:43 am, Kyle to Y-End station VEA area, working with purge air system.
11:48 am, Karen heading back from Y-Mid station.
12:12 pm, Kyle leaving Y-End station.
1:26 pm, Kyle to Y-End station VEA area, continue with work.
2:25 pm, Kyle leaving Y-End station.
3:35 pm, Kyle heading back to Y-End station, continue with work.
3:54 pm, Doug to the CS VEA, looking a small circuit board.

Following the measurement of the power recycling gain (alog 14532), I made an estimation of round trip loss in the power recycling cavity.

In order to explain the recycling gan of 21 for the 45 MHz sidebands, round trip loss needs to be 2.3%.

The plot shown above is power recycling gain for the 45 MHz sidebands as a function of round trip loss. The blue curve represents the one without losses but with the effect of the Schnupp asymmetry. The green one is that with all the known losses included.

For more details, see the attached python code. Also, the highest gain we can achieve is 42 for the 45 MHz without round trip losses. Note that I assumed both ITMs to have the same curvature and also I have not included the mode matching effect.

• Work permits update.
• Pcal group:to work on both systems the rest of the week, at both end stations, including laser activity.
• OpLev group: setting up assembly area, and assembly of damping components to be installed on piers.  Jeff K. to work on OpLev calibration.
• Report of Y-End station seismometer out, part of the LHO PEM system, Filiberto to look into it.
• SEI group: commissioning of sei-systems.

I restarted the DAQ at 10:40PDT Tuesday morning to connect the EDCU to the new Beckhoff channels (PCAL at EX,EY, OMC renaming at C1). After the restart we noticed that the ALS_COMM guardian was stopped. The log file gives the error "no NDS servers available" at 10:40.

Looking into the code, the DOWN state of ALS_COMM calls the cdsutils.avg for the DAQ channel H1:ALS-C_TRX_A_LF_OUT_DQ to average this channel over 0.1 seconds. This NDS call failed when the DAQ was restarted and ALS_COMM remained stopped until a RELOAD was performed at a later time.

Looking at the guardian logs, two other systems have shown "no NDS servers available" errors: ISC_DOF and LSC_CONFIGS. In these cases they were not associated with an NDS restart, and were immediately followed by a guardian RELOAD (within a minute).

J. Warner, K. Venkateswara

We tried sensor correction in Z direction on HEPI using the GND_STS, while keeping the X direction sensor correction on Stage 1 using the ground super-sensor. The two attached pdfs show the result before and after. The result is almost the same level of performance in both X and Z with some improvement in Oplev YAW motion at ~0.15 Hz with HEPI sensor correction. This probably reduces the Stage 1 Z actuation, hence reducing the Z to RZ coupling.

We will try the X sensor correction to HEPI in the afternoon, after install activity at EX is completed.

model restarts logged for Tue 21/Oct/2014
2014_10_21 09:42 h1isietmx
2014_10_21 09:44 h1hpietmx
2014_10_21 10:36 h1dc0
2014_10_21 10:41 h1dc0
2014_10_21 10:41 h1nds0
2014_10_21 10:43 h1fw0
2014_10_21 10:43 h1fw1
2014_10_21 10:43 h1nds1
2014_10_21 10:54 h1broadcast0
2014_10_21 15:43 h1fw0

one unexpected restart of h1fw0. Maintenance day modification of SEI ETMX and associated DAQ restart. Beckhoff duplicate channels resulted in two dc0 restarts.

Took the ITMX ISI down to load proper filters for the ISI-HEPI L4Cs.  Corrected the L4CtoCartesian matrix and made a new safe.snap.  Back and running under Guardian.  Safe.snap committed to svn.

Alexa, Kiwamu

We did three items tonight:

1. We tried the good IM4 YAW bias that Keita found out today (see alog 14567) by steering PR3/PR2 and IM4.
   • => failed and got confused. We set these biases back to the usual values.
2. We made a comparison of the DRMI spectra with and without the BS yaw oplev damping loop
   • => found that the BS yaw oplev loop was contaminating the length signals and also increasing the chance of the SRC hopping.
3. We checked tolerance in the angle of the SRC-related optics by intentionally introducing offset.
   • => BS was the most sensitive optic which let the DRMI enter the 01 mode instability with misalignment of about 0.2 urad.

(IM4 angle)

We aimed for -8000 counts in IM4 yaw bias which is the value that Keita found out to be good from the point of view of cavity loss. We did this by steering PR3 while keep closing the IM4+PR2 ASC loops for the input pointing with respect to the arm cavity. This resulted in yaw biases of -162.70 and 762.99 urad for PR3 and PR2 respectively. The original biases were -177.30 and 629.26 urad respectively. Since this resulted in misalignment in the POP beam, we had to steer some optics on ISCT1 to recover the light on the POP diodes.

However this resulted in a weaker light at the POP path, due to a clipping somewhere in chambers. The POP beam did not like a Gaussian beam any more and looked enlongated vertically. See the attached movie for getting idea of how it looked like. The movie shows the POP beam in front of the top periscope mirror on ISCT1. The power build-up in POPAIR_RF18 was smaller by more than a factor of 5. I think this is a clipping in somewhere in the POP path at the outside of the PR cavity because we could lock the DRMI without changing the LSC gains -- the optical gains stayed almost the same.

We decided to go back to the nominal angles and set PR2 and PR3 back to the usual values. We realigned the optics on ISCT1 again. 

One thing we got confused is that, after restoring PR2 and PR3 back to the usual values, the IM4 YAW bias did not have to move at all in order to get a good pointing toward the X arm. Maybe we simply do not understand what we are doing.

(DRMI length signals are contaminated by BS YAW oplev damping)

During the IM4 anlge study, we came up with a hypothesis that somehow the BS oplev damping loops were kicking the BS and let the SRC hop to some other modes. So we made a comparison with and without the oplev loops running. We found the following two facts:

1. BS YAW oplev damping loop was contaminatong the length signals at around 10 Hz
2. Engaging the yaw damping loop seemed to increase the number of hopping.

The plot below is the DRMI spectra with and without the YAW oplev damping loop. Note that the PIT loop was untouched and left on all the time during this measurement:

The ones in vivid colors (red, blue and green) are the spectra with the oplev loop running. The other curves are the ones without the oplev loop running. It is obvious that the noise between 4 and 20 Hz increased by some amount. In particular, the noise level in SRCL increased by roughly an order of magnitude. This contaminatin was repeatable.

(Tolerance in optics' angle)

We introduced intentional misalignment in the SRC optics in order to see how big misalignment they can tolerate. The below are the measured tolerance that gave us the 01-mode instability:

• BS = 0.2 urad
• ITMX = 0.5 urad
• SR3 = 0.5 urad
• SR2 = 4 urad
• SRM = 16 urad

All the numbers shown here is for the yaw direction. We did not measure it in pitch.

I found that the HAM2 ISI had been tripped at around 22:00 PDT probably because of me leaning against the HAM2 HEPI peer on the east side.

After I untripped the watchdog, the ISI had a difficulty coming back on its own under the control of the guardian. One time it failed during the X/Y/RZ gain ramping for some reason. I did not look into the detail. Also, in another time, it failed because GS13s saturated during the engagement of Z/RX/RY. Again I did not look into the details and don't know what specific state it was at when failing. Eventually, I decided to go through the process step by step by pausing the guardian at each step. However at this point, it smoothly went and it did not fail. Anyway it is back and running fine now.

J. Kissel, J. Warner, K. Venkateswara

Based on Rich's and Jeff's SEI log entry 586 and 594, we made a second attempt at sensor correction on ETMX along X and Z on stage 1, which seems to be working better. To judge the performance I have plotted the stage 1 T240 output and also the Oplev Pitch and Yaw output. We used a slighlty modified version of Rich's sensor correction filter described in the above log.

To establish baseline, the first plot shows the Stage 1 T240_X motin (green), the ground STS (blue) and the tilt-subtracted ground super-sensor (red) with no sensor correction applied. I've also shown the coherence between some sensors and the Oplev motion. All degrees of freedom had Ryan's LLO blend filters.

The next file (SensCorrectOnBRSOff) shows the sensor correction turned on for X and Z on stage 1, but with normal gnd_STS, not the tilt-corrected super sensor.

The final file (SensCorrectOnBRSOn) shows the sensor correction with the tilt-subtracted super-sensor for X. Note that the ground motion (blue) is not the same during these data sets, but the relative differences between the lines are important.

Some comments:

1. Based on these plots, it looks like turning sensor correction On, even without tilt-subtraction, improves performance at 0.1-0.5 Hz by factors of 2-5. It's effect below 0.1 Hz is not clear - there may be small tilt amplification. Switching to the tilt-corrected super-sensor slightly improves performance below 0.1 Hz by factors of 2 ish. It is probable that we are limited by tilt-reinjection from the low X blend.

2. We are probably limited by the L4C sensor noise between 0.5 to 1 Hz. By improving the L4C blend, we may be able to get another factor of 2ish at these frequencies.

3. The Oplev motion doesnt show much improvement despite better X performance. The pitch is very sensitive to and probably limited by the RY blend.

Sensor correction for X and Z has been left on overnight, since it may help. It is easy to turn off from the ISI medm screen, if it is affecting performance.

edit: I added the Stage 1 Z performance to the plots. The sensor correction appears to improve z performance by ~10 at the microseism. But there may be more pitch motion at ~10 mHz. Not sure what is causing that.

Tomorrow, we will try HEPI sensor correction which may or may not be better.

edit: I have added another file also showing the Stage 1 RY motion (converted to displacement units), which shows good coherence with X motion confirming tilt-reinjection in X.

I have mapped out the usage of the H1 science frame per subsystem. I also compared this with the frame usage estimation performed by Matt Evans and Peter Fritschel in T1000313.

The first attachment shows the H1 science frame data (uncompressed) usage in MB/s per subsystem.

The second attachment shows the H1 frame usage comparison between today's frame and the T1000313 estimates. I have normalized the estimate with the frame compression ratio to get comparable numbers. 

J. Kissel

Using the calibration calculated in LHO aLOG 14405, I've installed the new ETMY slider gains,
EY P =  19.341 [ct/urad]
   Y =  51.013 [ct/urad]
and saved adjusted alignment offsets for ALIGNED and MISALIGNED, confirming that the *output* of the OPTICALIGN bank is the same. After Jason centered the ETMY optical lever on the ALIGNED state (which had drifted way off, see LHO aLOG 14555), others needed the optic misaligned before I had the change to get measurements for refining the optical lever calibration. 

Will keep pecking away when time and commissioning permits, but still no refined optical lever calibration for the ETMs.

IM4 was scanned in YAW while the DC SUM of various sensors were recorded, and it's apparent that there's a clipping.

In the attached, red, blue and green represent normalized DC SUM of the POP_A, POP_B and AS_C respectively plotted against IM4 YAW slider offset. Blue vertical line at -8520.7 shows the alignment we were at this morning.

There appears to be a hard edge on the left side on the plot that is common to the sled and the AS_C, and I guess that's the baffle in front of the PR2.

We're already very close to the edge. From the red and blue data at the blue vertical line, the single trip loss is either 0.3% (red) or 0.7% (blue), and you need to double the number for a round trip loss.

If we go somewhat to the left on the plot, you're already dead. I propose to move somewhat to the right.

The fact that AS_C shows somewhat different pattern means that there's some other clipping going on for the SRC path, on top of the PR2 baffle.

In the plot, Relative power=1 simply means that the measured power was the highest.

Latest news from the OMC:

==== Beam stabilization at the dark port ====

To keep the beam centered on the both the AS WFS and the OMC, I recalculated the actuation matrix for the OMC alignment loops, following Koji's calculations in T1400585.  Instead of using OM1 and OM3 for the alignment control, now we use OM1 and OM2, so that all of the control is upstream of the WFS.  This works very well; the low-frequency beam motion on the WFS is suppressed by 10x or more.  In the first plot attached the solid lines (references) are without the OMC alignment loops engaged, the dashed curves are with the OMC QPD servo on.  It doesn't look as though ASC-DC loops from the WFS --> OMs are necessary, but this may change when the dark port is dominated by higher-order modes (all this work was in a single-bounce configuration).  In principle any motion of the OMC suspension relative to the WFS will not be suppressed, from the point of view of the WFS, since the OMC QPDs are on the OMC breadboard, and the WFS are fixed to the table.

Anyways if you want to keep the beam centered on the AS WFS, you can set the OMC guardian to the 'ASC_QPD_ON' state.  The guardian control should be robust in the event of locklosses (if there's no light on the QPDs it will run the OMC down script and wait for the beam to return).  Note that if cavities are moving through fringes this will screw everything up, so maybe it makes sense to have the OMC guardian managed by the DRMI when ASC loops are being tuned.

==== Offset locking state for the OMC (also some gain swapping) ====

To measure the length noise in the OMC I added another state to the OMC guardian, OFFSET_LOCK, that moves the lock halfway off-resonance.  The procedure follows what Zach outlined at LLO.  I found some gotchas that had to be solved: the high-pass filter on the input to the LSC demod needs to be turned off, and the DCPD normalization has a *lower* saturation limit at 0.1 that will totally ruin the DCPD NORM signal for small transmitted power on the DCPDs.  (The overall dc gain in the DCPD A and B filter banks is -122.4dB, so we hit the lower limit pretty easily.)  To keep us from hitting the lower rail, I moved a gain factor of 1000 from the DCPD SUM filter bank to the DCPDs themselves, this keeps the output of DCPD_NORM_FILTER above the lower saturation limit.  The NORM channel is used for the OMC LSC and the SUM (which previously had the 1000x gain, now moved upstream) is sent to the IFO LSC, but the change is common to both DCPDs, and the overall SUM signal hasn't changed, so this adjustment should be transparent downstream of the DCPD conditioning.

==== OMC stability over several hours ====

Last night the OMC was locked on a single bounce from ITMY for about eight hours.  The PZT control drifted by 2V, slowly approaching an equilibrium state, and there was no change in the transmitted power.  (There was a small earthquake just after 0900 UTC that caused some noise in the DCPD SUM.)  It relocked a couple of times on its own in the morning.  This is with the QPD servo enabled, not the dither, so the alignment stability is somewhat better than what we'll use for the full IFO.

A 2V change in the PZT drive corresponds to a 28nm change in the cavity length (from T1000276).  The DCPD SUM channel should be calibrated for mA (I think), and for a single-bounce beam with 10W input to the IMC there should be about 19mW at the dark port.  To do: calculate the expected change in cavity length and the time constant to see if this 2V shift in drive is what we expect from thermal expansion of the breadboard.

==== OMC LSC demod phase ====

I repeated Nic's measurement of the demodulation phase for the OMC LSC dither loop.  With the OMC LSC loop open, I moved the PZT slightly off resonance, turned on a 100Hz excitation in PZT1, and adjusted the demod phase so that the ratio of the I-phase / Q-phase was maximized.  I found a phase of 70deg was optimal; this is quite a bit off from Nic's observation of 120deg.  I'm not sure how different our methods were, or whether a drift of ~50deg over ~2 months is something we should expect.  We'll keep an eye on this phase and see if it keeps changing.